bluetone amps -> FET emulating amps

[slajeune]

While reading this month's Vintage Guitar (I can always dream...), I read an article about blueton amps ( http://www.bluetoneamps.com/ ).  well, from reading the article, it looks like they are simulating the tube sections with FETs.....

Hum.... Were did i see this  :lol:

Once again, kudos to the guys at runoffgroove for giving us such good circuits and ideas!

Cheers,
Stephane.

[cd]

This is really nothing new.  Companies have been trying to replace tubes with transistors for 30+ years.  IMHO this is a niche product at best.

[slajeune]

Hi cd,

you're right, companies have tried to replace tubes with transistors.  But the article stipulates that the valve circuits are duplicated directly using FETs, just like the ROG emulators.  That's why I was pointing this out.

Cheers,
Stephane.

[cd]

Yeah Roland tried to do that years and years ago.  Same with Sound City, or one of those '70s off-brands.  ROG deserves praise for popularizing FETs within the DIY community but it's been around for a long, long time - I'd call this bit of convergent evolution coincidence.  Think about it: if you could replace a $10 tube with a 50 cent FET, don't you think we'd all be using FETs by now?  Well, that's a dumb question since guitar players are the most notoriously conservative people when it comes to gear

I call these things "niche products" since as long as the big names continue to use tube amps for recording and live performance, and tubes continue to be relatively cheap, players will always lust after and call tubes THE sound.  It's like cars in North America: gas is still relatively cheap (around 60 cents/litre $US on average) and most people like big cars with big engines, even if they use stone-age technology (like GM and their push-rod engines).  The occasional greenie will drive a hybrid or small/efficient car, but most people, given the $$ expense, will drive a big gas guzzler.

Yeah, I know the analogy doesn't hold for Europe, so sue me

[RDV]

Well, I'm using a bunch of $.50 FETs to make my tube amp sound better. A well designed SS amp can sound really good. I've also played through some terrible sounding tube amps. I'll go for anything that rocks!

RDV

[aron]

Many thanks to RunOffGroove BUT please you new guys, many people have contributed this sort of cool idea BUT Jack Orman was the one that made this mainstream for us.

His use of FETs and his Mini-Booster and later "amp style" circuits were the inspiration for all of us.

[Ed G.]

The clips sound kind of fuzzy and compressed. Which is good for when you like that sound, but I don't hear a good semi-clean tone, which is what I was expecting.

[B Tremblay]

Many thanks to RunOffGroove BUT please you new guys, many people have contributed this sort of cool idea BUT Jack Orman was the one that made this mainstream for us.

Exactly.  All we did was take the same approach that Doug Hammond used for his Meteor and then apply it to a few of the more popular vintage amps.

[Doug_H]

;lkj

[aron]

>All we did was take the same approach that Doug Hammond used for his Meteor and then apply it to a few of the more popular vintage amps.

But you do it so well too!  :wink:

[tcobretti]

The thing about the whole jfet/tube connection is that manufacturers DON'T seem interested in them at all.  I recently demoed a Vox Pathfinder 15.  It's a small 15w ss amp that sounds horrible.  The whole time I was trying it I was thinking, "why doesn't vox get a jfet ac30 emulator and use it as the preamp of this thing?"  I would have bought one in a second if it was a 15w vox english channel.

If marshall, vox, and fender made small amps that soundled like the ROG pedals do, I'd probly buy one of each.

[Prive]

Hi everybody!!!!

If Fender, Marshall, Vox, Mesa and others build small and cheap amps that sounds really great, why to pay 2000 in a big, heavy one?

That is the answer to me.

:shock:

Saludos, Marcelo.

[cd]

Prive, if a cheap SS Fender sounds great to you, more power to you.  Count yourself lucky that you'll never lust after a $3000 Matchless.

As for the Pathfinder 15 - I didn't think it sounded THAT bad.  Decent cleans, horrible OD, but that's typical for an amp in its price range.  Mind you I'm not nuts about the English Channel either.  Bottom line, it's cheaper for Vox to build an amp around 2 opamps and a power amp chip (open up any of those small practice amps, that's all that's in there) than to use multiple FETs.  And as DSPs get smaller and cheaper (emphasis on cheaper) the part count will be even further reduced.

If it sounds like I'm slagging the ROG designs, I'm not.  They're nice for what they are (small, easy to build, low cost, low maintenance) but I'm sure anyone who has played the real thing will tell you they only capture the general vibe of an amp; all the subtleties that make an amp special are missing.

[spongebob]

http://www.bluetoneamps.com/vvt.html
"In Blue Tone Virtual Valve Technology amplifiers each triode stage is simulated by a FET and connected together in the same way as the early valve amp designs, i.e. using AC coupling and minimal feedback. The power stage is also accurately reproduced including simulation of the transformer and it’s interaction with the loudspeaker (i.e. low damping factor). This process is at the heart of the overdrive sound because in early valve amplifier designs the overload distortion is produced at the output stage not the pre-amps (unlike many modern high gain valve amplifier designs)."

My first guess was that they use a chip amp as the output stage as in many solid-state amps, but after reading this section I'm thinking it must be a little bit more sophisticated! Any ideas how this is done?

[Prive]

Prive, if a cheap SS Fender sounds great to you, more power to you.  Count yourself lucky that you'll never lust after a $3000 Matchless.

Sorry, you must don't understand me, my english sucks, i speak spanish.

I've been trying to say that that companies will never lost money for a practicing musician, not that i like small amps more than biggest.
I have a little Peavey Rage 158 trans tube for practice but my mean amp is a 100W super lead wit lots of mods, i need the lows for Fuzzed drop C riffs.

Sorry again for my Tarzan's english  :shock:

Saludos, Marcelo.

[Ge_Whiz]

A well designed SS amp can sound really good. I've also played through some terrible sounding tube amps. I'll go for anything that rocks!

RDV

Thanks for telling it like it is, RDV - this quote should be in the FAQ.

[Ed G.]

Peavey's solid state amps are pretty darn good sounding for what they are. A lot of people have played those things for years.
A while back the PV amp to have was the Stereo Chorus 212. It had incredible gain. A real 'rocker's' amp.

[bluetoneamps]

http://www.bluetoneamps.com/vvt.html
"In Blue Tone Virtual Valve Technology amplifiers each triode stage is simulated by a FET and connected together in the same way as the early valve amp designs, i.e. using AC coupling and minimal feedback. The power stage is also accurately reproduced including simulation of the transformer and it’s interaction with the loudspeaker (i.e. low damping factor). This process is at the heart of the overdrive sound because in early valve amplifier designs the overload distortion is produced at the output stage not the pre-amps (unlike many modern high gain valve amplifier designs)."

My first guess was that they use a chip amp as the output stage as in many solid-state amps, but after reading this section I'm thinking it must be a little bit more sophisticated! Any ideas how this is done?

Hi,

This is Dave Robinson from Blue Tone Amplifiers in the UK.  A customer from the States sent me the link to your thread.  I asked Aron if it would be okay to post on here.

Our amp emulates valve amps in a new way which, as you've suggested, is more sophisticated than previous designs (a closely guarded secret!).  For marketing purposes we've chosen to call this 'Virtual Valve Technology', but in essence it is exactly that.  The amp sounds and behaves like a vintage valve amp.  Regarding an earlier comment about 'semi-cleans', in fact this is one area where the amp excels, as John Jorgenson noted after he had tried the amp when he was over here touring recently.  I know we need to update and improve the sound files and we will do that very soon.

Our experience so far is that guitarists are quite conservative where amps are concerned, and many have prejudices which will be difficult to overcome in the short term.  We need to convince players that they really don't need to buy a 50w head and 2 x 12 cab to play in the local pubs and clubs, never mind at home or in the studio; our amp provides that 'big' valve sound at more practical levels without sacrificing tone - in our humble opinion, of course (Pete Townshend used his Blue Tone during recording sessions for 2 new Who songs recently).

Anyway, look out for full reviews of the amp in Guitar Player, Vintage Guitar and Guitar World shortly.

Many thanks for your interest.

Dave
www.bluetoneamps.com

[StephenGiles]

Prive - your English is very good, just like the meat from this Asado!!!

Stephen

[R.G.]

"In Blue Tone Virtual Valve Technology amplifiers each triode stage is simulated by a FET and connected together in the same way as the early valve amp designs, i.e. using AC coupling and minimal feedback.

There is a semi-large number of designs going back to the late 60's doing this. It can sound OK, and as always, if it sounds good do it. However, if you think you can directly replace a 12AX7 section with a FET, even scaling the voltages down and messing about with the parts a bit, you are most likely to be disappointed. How do I know this??? Um... I did it back in the mid 70's, and I have some schemos from commercial attempts at it.

It is, as stated, a simulation. Naugahide is simulated leather. Particleboard furniture with melamine woodgrain printed covering is simulated fine hardwood furniture.  The quality of a simulation is how well it fools you into believing that it is something that it is not, by definition.

FETs can sound good, but use them because they sound good, not because they are almost but not quite tubes.

The power stage is also accurately reproduced including simulation of the transformer and it’s interaction with the loudspeaker (i.e. low damping factor). This process is at the heart of the overdrive sound because in early valve amplifier designs the overload distortion is produced at the output stage not the pre-amps (unlike many modern high gain valve amplifier designs)."

Well plowed field. See  http://sound.westhost.com/project56.htm for discussion of the history and a way to diddle with the output impedance of an amp.

My first guess was that they use a chip amp as the output stage as in many solid-state amps, but after reading this section I'm thinking it must be a little bit more sophisticated! Any ideas how this is done?

Your first guess was probably almost right; see the web page above. Even if the amp is discrete or semi-discrete, the opamp principles that let you do variable impedance still apply.

I'm guessing that the only elaboration they have made beyond the higher output impedance by current and voltage feedback is some kind of soft clipper in front of the power amp to simulate (see above) the distortion process as a tube power head runs out of headroom. This could be as simple as a diode clipper or more complicated. See my comments on the Thomas Vox "limiter" circuit on the Thomas Vox amps from the 1960's.

Simulation amps are interesting, but they need to stand on their own sound, not how close they are to tubes.